The subject of the invention is a static device maintaining homogeneity of a mixture of powders subjected to gravity flow.
It is sometimes necessary to ensure the flow of mixtures of powders whose components have very different characteristics of density, granulometry, specific surface area, etc. Samples can be taken at different points on the path followed by the mixture in order to verify that its homogeneity is being maintained: it has in fact been found that segregation of at least some of the components of such mixtures arises very easily, which will compromise the quality of the manufacturing process and use of the mixture. This loss of homogeneity was produced in particular in the vertical sections of the flow paths, when the mixture was subjected to a free fall, probably because of the various effects of air resistance on the different components.
Solutions of different kinds have already been proposed in order to keep the powder mixtures homogeneous: some consist in treating the mixture itself, by choosing components having similar characteristics or by adding binders which provide cohesion of the different components, but these solutions which have a consequence for the composition of the mixture are constraining; mechanical devices have also been proposed, such as vibrating passages, mixers with screws, rotating spirals etc, placed at suitable points on the path followed by the mixture in order to produce stirring movements therein and to maintain its homogeneity or at least to re-establish it, but these motorised mechanical means complicate the device and make it more expensive.
A part is proposed here which can be used at the location of the vertical sections of the flow path, and whose advantage is in maintaining the homogeneity of the mixture by constant stirring and by means which are entirely static, and which therefore require no maintenance.
The vertical flow path is then delimited by a device composed essentially of a series of separate channels laterally inclined in opposite directions, each of the channels extending in a direction intersecting a channel immediately below.
This arrangement is similar to that of the document U.S. Pat. No. 2,502,341, designed in particular for coffee grains, but the invention is distinguished from the prior document by other characteristics: channels are formed by plates broadening and curving more towards the bottom, which reinforces the stirring of the mixture flowing over them; in addition, a pipe also delimits the flow path and contains the channels: the interior of the tube is partitioned and divided into compartments which prevent the dispersion of the finer particles, which tend to remain in suspension.